Had a similar situation several years ago with a machine in the plant it would not give the same results as other machines with the same settings. We did a bunch of voltage and amp testing on the machine checked some parts and replaced some and could not get a good handle on what was going on. We ended up finding a connection in a twist lock connector on the incoming power that was not tight. We could test it and get the correct rated power by testing it at the plug. We finally found the problem testing the incoming voltage when the machine was under a load and had a voltage drop on one leg of the incoming power. Tightened the connection and everything worked as it should. Sometimes it is just simple stuff that makes things not work right.
This may or may not be your problem but thought this might be something to try.
PowerTig 200DX
Supercut 50P
PowerTig Micro 185 SOLD GREAT MACHINE
Millermatic 200
Miller Thunderbolt
Jet 1340 Lathe
Jet 20" Drill Press
Jet 12" Wet Band Saw
Kalamazoo H7 Bandsaw
Forward 12,000 lb 4 Post Lift